BACKGROUND:  Polyaniline nanofibers are among the most useful of conducting polymers due to their environmental stability and simple acid-base doping/de-doping chemistry. These nanostructures exhibit superior conducting and photothermal effects. A problem in processing polyaniline nanofibers is aggregation. Strategies for preventing aggregation are to coat nanoparticles with foreign capping agents and/or add surfactants.

INNOVATION:  The innovation involves a new understanding into the process of aggregation. We have learned that the nucleation of nanoparticles plays a crucial role. Self-stabilized polyaniline aqueous colloids can now be obtained by purifying chemically prepared nanofibers and controlling the pH. We demonstrate the ability to form stable polyaniline nanofibers without the need for stabilizing agents. Thick films can be fabricated from colloidal dispersions through casting, while monolayers can be created by electrostatic self-assembly.

DEVELOPMENT-TO-DATE:  Polyaniline is formed using aniline, ammonium peroxydisulfate, and HCl. Other doping acids can be used as well. Washing and centrifugation lead to pure nanofibers. Colloidal stability is dependant on concentration but we have experiments showing stability up to at least 2 months at an optimal pH level. A thin film is formed by dipping a glass slide or silicon wafer into a dilute stable colloid. SEM observations show a continuous conducting network of nanofibers.

Reference: UCLA Case No. 2006-134